Method and apparatus for impregnating strip stock



N N A M A. c.

`METHOD 'AND APPARATUS FOR IMPREGNATING `STRIP STOCK Filed April 3, 1944 ATTORNEYS Patented Aug. 6, 1946 METHD AND APPARATUS FOR IMPREG- NATING STRIP'STOCK Cecil A. Mann, Dayton, hio, assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application April 3, 1944, Serial No. 529,324

7 Claims. 1 Y

This invention relates to a method and apparatus for continuously applying soft or lower melting point metal to the surface of a metallic strip, and is more particularly concerned with the method and apparatus for continuously applying and simultaneously impregnating porous metallic strip material with a lower melting point metal.

An object of the invention is to provide a method and apparatus whereby porous strip mae terial or composite strip material which includes a porous metal layer thereon may be continuously impregnated under' sub-'atmospheric conditions.

In carrying out theabove object, it is a still further object of the invention to carry out the vacuum impregnating step while the strip material is substantially in the ilat condition.

This applicationis a continuation in part of my copending application, Serial No. 376,512, directed to a method and apparatus for appli/insr molten metal on strip stock. This application is directed to somewhat similar subject matten-but is modified with particular respect to the Vacuum impregnating step and apparatus whereby the apparatus is simplified to some extent.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompany-4 ing drawing wherein preferred embodiments of the present invention are clearly shown.

In the drawing:

The drawing shows a diagrammatic View of a vacuum impregnating apparatus showing the various pumps and conduits with a strip being run therethrough.

Referring particularly to the drawing, a vacuum impregnating apparatus is shown at 20 which includes an elongated tunnel-like structure broken ldown into three main sections7 namely, the rst section 22, a vacuum chamber 24 and a third section 26. Sections 22, 24 and 26 are aligned and contain entries and exits so that a strip 30 may pass therethrough in a substantially at condition. Strip 36 enters chamber 22 through an entrance 32 and leaves through an opening 34 which is an entrance to the vacuum chamber 24. It then passes through the Vacuum chamber and leaves said chamber through exit 36 which is the entrance to chamber 26. Finally the strip passes out of chamber 26 through exit 38 .Chambers 22 and 26 contain a predetermined volume of molten metal 46, in this case babbitt, the height of which is controlled by weirs 42 and 44 respectively. When the level of babbitt exceeds the level of the weirs, the excess babbitt is drained back to a supply tank 46 through conduits 48 and 50 respectively. A supplytank 46 contains a substantial volume of babbitt 40 and also is provided with heating means, not shown, for maintaining the babbitt in the molten condition.

In order to supply babbitt to chambers 22 and 26, the supply tank 46 is provided with two pumps 52 and 54 respectively. These pumps convey babbitt from supply tank 40 upwardly through supply conduits 56 and 58 to chambers 22 and 26 respectively. The pumps 52 and 54 have sulcient pumping capacity to always maintain an excess of babbitt ilowing into the chamber so that there is always a return of babbitt through conduits 48 and 56. It is also apparent that there will be a leakage of babbitt around the entrance 32 and exit 38 of the apparatus, which babbitt is likewise suitably conveyed back to the supply tank 46.

The intermediate chamber 24 is evacuated by means of a vacuum pump 66 which cooperates with the second pump 62 that is immersed in the babbitt supply, Pump 62 is utilized to return babbitt leaking into the vacuum chamber 24 through openings 34 and 36. Thusthe pump 62 while pumping babbitt into the supply tank 46 also induces a vacuum on the intake side thereof which cooperates with pump to produce a very high vacuum in the chamber 24.

It is preferable to supply a reducing gas to chambers 22 and 26 to maintain as clean a condition as possible on the surface of the babbitt whereby oxidation is reduced, if not eliminated. This lessens the amount of sla-g formed and eliminates the possibility of clogging of the pumps. In this instance the supply tank 46 is closed to the atmosphere and may either be supplied with a reducing atmosphere thereover or the molten babbitt may be protected by flotation cf a refractory material such as bentonite en the surface thereof.

The pumps 60 and 62 maintain a pressure of about 2 to 3 mm. of Hg abs. in the vacuum chamber. Reducing atmosphere is admitted to this chamber through conduit 63 in suicient quantity to bring the pressure in the Vacuum chamber to about 7 mm. of Hg abs. The reducing atmosphere prevents any oxidation of the babbitt in this chamber. .y

In operation, the device is similar to the device shown in my copending application, Serial No. 376,512. Strip 36 enters the apparatus through the entrance 32, having rst had the surface thereof cleaned of any oxidation, dirt or grease by means of a suitable fluxing apparatus, several embodiments of which are shown in my copending application above referred to.

The strip 3i) includes at least a portion thereof of porous material which requires impregnation. The strip enters under the surface of the babbitt 4D in chamber 22 and partial impregnation is obtained. This portion of the strip then progresses into the vacuum chamber Where any gasY remaining in the pores escapes due to the rarefaction of the atmosphere thereover. This causes an impregnating of the babbitt into the pores to replace any gas which Was evacuated therefrom. This portion of the strip then progresses into the chamber where it enters under the surface of the babbitt, and additional babbitt is thereby supplied to complete the impregnation. The strip then passes out of the exit 3B into a suitable casting apparatus, not shown, but described in detail in my copending application Serial No. 376,512. 'Ihiscasting apparatus permits any desired thickness of babbitt to be cast on the strip,V but forms no part of the present invention.

It is manifest fromY the foregoing that a complete impregnationA can be obtained in this apparatus without any bending of the material'. This is particularly necessary when operating on heavy strips Where the cross sectioned area of the strip is such as to make bending difcult or impossible. The entire operation therefore is carried out continuously While the strip remains in a flat condition moving in a single plane.

It will be noted that the use of pump S2 eliminates the necessity of the sump and barometric leg utilized in my copending application 376,512 in that the intake side of the pump balances the vacuum in chamber 2d so that pump 62 cooperates with pump 69' to produce the desired vacuum. Furthermore pump 62 has the additional function of removing the babbitt from the vacuum chamber which babbitt has flowed or leaked therein from chambers 22 and 25 in returning same to the supply tank G5.

It is manifest that in place of babbitt any other lower melting point metal may be utilized, lead, tin, antimony, aluminum, or alloys thereof may all be used with porous strips having a higher melting point whereby substantially complete impregnation is possible.

While the embodiments of the present invention as herein. disclosed, constitute preferred forms, it isl to` be understood that other forms might be adopted, all c-oming Within the scope of the claims which follow.

lVhat is claimed is as follows:

l. In a machine for continuously impregnating porous strip material in the substantially flat condition, an impregnating chamber including throat portions at either end thereof for restricting the now of impregnant therefrom around a strip passing therethrough, a communicating vacuum chamber at the egress end of said rst chamber, means for partially evacuating said vacuum chamber, and a second impregnating chamber 4 leakage into the vacuum chamber and out of the machine, and means cooperating with said rst mentioned means for partially evacuating said vacuum chamber and for returning the impregnant which leaks out of said throat portions to said supply tank.

2. In a machine for continuously impregnating porous strip material in the substantially nat condition, an impregnating chamber including throat portions at either end thereof for restricting the flow of impregnant therefrom around a strip passing therethrough, a communicating vacuum chamber at the egress end of said first chamber, means for partially evacuating said vacuum chamber, and a second impregnating chamber connected with the egress end of said vacuum chamber and including throat portions at either end thereof for restricting the now of impregnant therefrom around a strip passing thereconnected with the egress end of said Vacuum chamber and including throat portions at either end thereof for restricting the iiow of impregnant therefrom around a strip passing therethrough, a supply tank for containing the impregnant, pump means for pumping impregnant to each of said impregnating chambers, said pump means having suicient capacity to maintain a defined level of impregnant in each of said chambers abovelthe level of isaidstrip regardless of the through, a supply tank for containing the impregnant, pump means for pumping impregnant to each of said impregnating chambers said pump means having sumcient capacity to maintain a defined level of impregnant in each of said chambers above the level of said strip regardless of the leakage into the vacuum chamber and out of' the machine, means cooperating with said rst mentioned means for partially evacuatingsaid vacuum chamber and for returning the impregnant which leaks out of said throat portions to said supply tank, said last named means being immersed in said impregnant, supply means for providing a reducing atmosphere over the impregnant in said two end chambers and for providing a measured predetermined pressure of reducing atmosphere in said vacuum chamber.

3. An apparatus for continuously impregnating metallic strip material including a porous metal layer thereon, said material being in a substantially flat condition during the imp-regnation thereof, comprising in combination; a babbitt chamber adapted to be partially filled with bab.- bitt through which said strip may pass and including Ythroats at either end thereof Which closely lit the strip as it passes into and out of said chamber; a communicating chamber at the egress end of said rst chamber adapted to be evacuated; means for partially evacuating said communicating chamber, a third chamber at the egress end of said second chamber and including throat portions at either end thereof, said third chamber also being at least partially filled with molten babbitt; a heated supply tank for holding an adequate supply of molten babbitt metal there- 1n; pump means connected with said supply tank and with said rst and third mentioned chambers for maintaining the level of babbitt insaid rst and third chambers substantially constant and above the surface of the strip, whereby the molten babbitt maintains a vacuum seal at the egress end of the said first chamber and. at the egress end of said second chamber; return means connected with said rst and third chambers for returning excess babbitt to said supply tank, a second evacuating means for partially evacuating said commimica-ting chamber, said last means also having the dual function of pumping babbitt fromv the communicating chamber to said supply tank, said two means. for'partially evacuating the communieating chamber cooperating to produce the de-V quantity being predetermined so as not to re'- duce the vacuum appreciably.

4. An apparatus as claimed in claim 3 wherein weirs are provided in said rst and third chambers to maintain the desired level of babbitt therein.

5. An apparatus as claimed in claim 3 wherein heating means are included in said rst and third chambers for maintaining the babbitt in a molten condition.

6. An apparatus as claimed in claim 3 wherein said rst chamber includes a xed Weir for maintaining a defined level of babbitt therein and wherein said third chamber includes an adjustable Weir whereby the babbitt level in said third chamber may be maintained at any desirable depth.

'7. In a' method of continuously impregnating porous metal strip material in a substantially flat condition, the steps comprising: providing two impregnating chambers containing molten impregnating metal, providing an intermediate vacuum chamber connecting said impregnating chambers,

all of said chambers being in substantially the same horizontal plane and so constructed that f leakage can occur from said impregnating charnbers into said vacuum chamber around said strip, passing said strip through' al1 of the chambers in substantially flat and unbent condition and in a single horizontal plane and beneath said impregnant in said impregnating chambers, supplying sufficient impregnant to each of said impregnating chambers to maintain the level of molten metal constant so that the impregnant leakage from said impregnating chambers into said Vacuum chamber is compensated for by the new irnpregnant being supplied into said chambers whereby a seal is maintained between said chambers and said vacuum chamber and finally removing said leakage from said vacuum chamber whereby the evacuation from said chamber is at least partially accomplished by removal of said impregnant therefrom.

CECIL A. MANN. 

